Phosphinoborine compounds and their preparation



' alkaline earth metal borohydride; If the bvorohydride is 2,925,440.that of ametalother than an; alkali metalor alkaline a Y i 5 earthmetal, it should be a volatile metallic borohydride, P PWE S P Also, aphosphine haloborine may be dehydrohalogenated Anton B. Bnrg, LosAngeles, and Ross-I. Wagner, Monte bello, Califi, assignors, by mesneassignments, to .iAmerican Potash & Chemical Corporation, a corporationof Delaware a No Drawing; Application June 17,

" Serial No. 666,213

17 claims. c1. 260 -6065) p This application, which isacontinuation-in-part of our copending application, Serial No. 446,147,-filed July '27, 1954, 'relates in general-tophosphinoborine polymersderived from [H PBH l and to their production. A

divisional application of the aforementioned Serial No. 1 446,147,,whichuis identified as 'application,Serial'-,No. 2o

' polymeric materials. Rings may also form of consider- 754,9l4, filedAugust 14, 1958, describes and claims .com-v pounds similar ..to thoseclaimed herein. More. particularly. this invention relates to suchphosphinoborines whereinatleast one of theuhydrogen atoms on thephosphorus or boron is replaced with certain monovalentor divalentcyclic organic radicals.

polymers; and plasticmaterials arej organicin nature and. may displayunsatisfactory chemical and H thermal sta-. bility under conditions ofspecialized usage. 1 M '3 It is therefore an ob'ect of th' inventiomtoprovideya group of basically. inorganicpolymers having unusual chemicaland thermal stability;

A further object of this invention is meth- 4 'odsfor synthesizingphosphinoborine polymers.

.,Ancillary objects and 'advantagesof this invention, if

notispecifically set out, will'become apparent during the course of thedetailed descriptionwhich follows. f j h Broadly, it has been found thatpolymeric phosphinoborines may be prepared which are unusually stable;They have the general formulae:

[RR'PBR"R"'],, wherein the symbols R, R, Rf and R? representfH,aliphatic substituents or aromatic substituents, at least one of R, R,R" and'R representing an alicyclic or aromatic substituent; and:

wherein the group RP designates'a heterocyclic ring including the Patom. R thus represents aportion of a larger. PreferablygR and-R of thefirst formula repre- 5 sent. alkyl groups having less than 13 'carbonatoms,

' lower cycloalkyl; phenyl, lower alkylesubstitutedphenyl, biphenyLornaphthyl and R" and R represent hydrogen, lower alkyl or. phenyL-itbeing home in mind that at least one of the symbols R, ,R., R" and R,"mustrep United i 7 2!? Thematerials ordinarily usedini-the preparation;of

E Patented Feb." 9 60 to yield the desired phosphinoborine.

More particularly, the phosphinoborines of this invention may be ofseveral varieties. Three or more individual 'RR'PBRR"' units may join toform a ring. a material, the most elementary of which, the trimer, isset; forth below: h I

la-law I R!!! V I I V Substances'of this type will be termed hereinafterring ably greater size, for example,"four-of-the RRPBR"R' units may jointogether to form'a tetramer corresponding to the trimer set forth above.7

-In order to be a ring material of this type, itis essential thatthecompound under consideration have no free hydrogens on-the phosphorusatom; Ifunreplaced'hythe equation:

drogens appear on the phosphorus, the product will not be'the. ringmaterial set forth above, but rather will be a linear polymer having aseries of phosphinoborine units joinedone to another through adjacentphosphorus'and boron atoms whereby toform an extended chain.

. The preparationjof these phosphinoborines can be ac complished inseveral ways. In one, certain secondary phosphine borines may' be"pyrolyzed to eflect the loss of one hydrogen. eachf from both thephosphorus and boron atoms.

wherein n' indicates the number of molecules present initially. Allotherfsymbols are used as in the general formula above.-

Itis to be noted in the equation above that the compound pyrolyzed hasonly hydrogen atoms adjacent the boron (excepting the P). Actually, itis possible to secure a 'certain amount of the desired phosphinoborinefrom a phosphine borine where one or more organic radicals are attachedto the boron in place of the hydrogen. However, this is not thevpreferred method of producing these materials since the pyrolysis of aphosphine borine having one or more aliphatic radicals on the boron atomresults indisproportionation which changes the phosphine'borineinitially present to dialkylphosphine trialkylborines anddialkylphosphine monoalkylborines attempera'tures below those requiredfor. the loss of .hy-

drogen from the RR'HP:BHR"R" reactant. Thus, for

60 example, wherethe compound (C H HP:BH(CH is resent one of thenamedalicyclic or: aromatic substi tucuts. Where R represents acyclopoly'methyleneradical,-

there preferably are between three and six carbon atoms in the chain.The products can be prepareditlirough a variety of methods. A secondaryphosphineborine,hav-

ing three hydrogen om on he Be r efp' rq d 5 whereby to split off onefhydrogen atom-from, both the,

phosphorus'and the boron atoms with thefipr'oduction of" the desiredphosphinoborinef Alternatively, the desired phosphinoborine,maybeprepared byfreacting a;phos-.. T phonium halide with aborohydride ofametal such as aluminum or, preferably, with an alkali-metal -oranpyrolyZF dr quantities. of (C H HP:'BH CH are obtained attemperatures'below those required for the obtaining of thephosphinoborine by the loss of hydrogen from the diphenylphos- Further,a certain amount of further disproportionation. whereby (C H PBH and" CH PB(CH units are formed is observed. And, [since the formationof someB(CH .in the early stages of the process results in partial suppressionof the disphine dimethylborine.

proportionation -atlater stages, it is found that a mixture ofpolymersand .copolymers 'of which (CH PBHCH v -units-predominate *with'some (C H ),PB(CH units The reaction proceeds in according with (Cal I5)HP I B )3 .and e and still lesser quantities of -(C H PBH units presentis obtained.

The most significant disproportionation reaction may be representedgenerally by the following:

4 having unsaturated substituents, this particular method is especiallyrecommended. It does not. necessitate the use of high temperatures whichtend to saturate any unsaturated groups on the phosphorus or boron. Asthe 5 reaction is not carried out at reflux'temperatures, a wide varietyof solvents such as any of the ethers maybe 2 employed. For example,diethyl etheris readily avail- 2 I able and is recommended for :use inthe process. Another followed by a loss of H to form phosphlnoborines:suitable solvent is benzene.

' a In using the dehydrohalogenation method as set forth n RR HPzBHgR (R2 above, it is important that the halogens'be either chlorine, bromineor iodine. Fluorine will not work and is not to n v be used in theprocess. This is because of the fact that n RR HP'BHZR I +-nIH2 HFbehaves unlike the other hydrohalogen acids. Either The fol 5 it willnot combine with a weak base so as to term an g i f g%ii ii- 353 2 12 3523 insoluble substituted ammonium fluor de or will commers, some ofwhich may not be the desired material is bme so weakly as not to carrythe reaction forward. ObtainecL Accord ngly, HF cannot be extracted fromthe P:B com- The pyrolysis may be carried out in a refluxing solventplex m a weak ternary mum of the ityp? Suggested of high boiling pointsuch as n bntyl eth t i h l .altronger base cannot f l di as an glycoldimethyl ether. However, where pyrolysis is to be alkah the Weakerrphosphl-n-e base will be displaced used, th pr f d method ofpyrolyzl-ng phosphine from the pnosphme borine add1t1on compound. brines does not necessitate the use of a solvent. Refiux- Cons-1 denngnow the linear polymers these may ing the phosphine borine itself in aninert atmosphere is prepared-by the methods set fom-ljabovel For exampan extremely Simple way to remove the hydrgen. No 25 the reactionbetween a phosphonium halide and a bone- Product contamination isobserved where this method is d f of an alkiah or alkahne earth metal ora volaulq used. Refluxing until no further hydrogen evolves genmetaihcboro-hydnde may be employed Where the phos' erally takes a Period ofabout to 60 minutes as conphomum halide has at least three l-lydrogimson h phos' trasted with periods measured in hours where a solvent phorusthe theyhosphinoliorme Product i is 1 It is advantageous 6 pass the H2evolved 30 tamed will be linear mater1al-as it will continue to bear bythe reaction into a mercury bubbler-thus afiording {at least onehydrogen on the Phosphorus The reacilon a ready method of ascertainingwhen the reaction is 15 F that set forth. h use phosphomum complete.Alternatively, the pyrolysis may be carried halide i bomhy-dnde{epreseming a-hydrogen ti fl system 7 atom. Similarly, thedehydrohalogenation method set In the second method, a phosphinoborineis prepared forth as the third method above m bc used and m by reactinga phosphonium halide with a borohydride of equation fq'that procedure Rrams-ems l i n' In an alkali metal, an alkaline earth metal or avolatile .me- 9 q R represgmilygmgenfm W -Q event tallic borohydridesuch as aluminum .borohydride. The the phosphmobonne P t W111 have twQhydrogen? reaction proceeds in accordance with the equation: 40 gg P g bth I v epractlce o is lnventlon 0 wt respec o peryn (RR PHZVX +11.1V{ 4)n forming the processes and securing the products thereof; '11 b come-aarent from .th followin exam les which RRPBH 'MX 2 n W1 s P n W 2 aresetforth by way of illustration. In the above equation, ,y is a smallinteger correspond- Example I Y XY P Ph II .ch de ing to the valence ofM, which preferably represents [(CGHH'MHZPI] lithium, sodium, potassium,calcium, magnesium, barium, strontium or aluminum and X is a halogen.The addiw K l -h qm -5 was plafed F a 4 tional symbols are used in thefashion indicated pref am k prevwusly h d Wlth i k, viously. 50wasfitted w th a .reflux condenser, a stirrer, and an addi- In the thirdmethod, the dehalogenation of phosphine tlon funnel- Dleihyl ether h jhaloborines, the rea tion proceeds: added to the reaction flask. Lithiumborohydride,

' Li+BH n(RRHP:BR"RX)- [RR'PBRR"],,+nHX in the amount of 0.22 g.dissolved in 10 ml. of diethyl wherein X designates a halogen and eachof the other ether was added w y o the r a tl flask: The flask symbolsare d i h manner Set out b T was heated for 40 minutes to reflux andlithium chloride the by-product HX is a hydrohalogen acid. This isprewas filtered from a reaction mixture when hydrogenno vented fromdisplacing the weaker acid function repreg r l The ol n wasremoved y twnsented by the boron atom and H or other radicals which at d P F A gYleld Q the d y y may be adjacent thereto (excluding the P) by providingphosphinoborine polymer [(C H PBH2],,, was thus a quantity of a tertiaryamine in the reaction vessel. obtained. The compound is a colorlesscrystalline solid. This reacts with the hydrohalogen acid and so removesExample 1 above relates to a process utilizing a phosit from thereaction mixture as a substituted ammonium phonium salt. Stoichiometryfor additional runs utilizing salt. Where it is desired to preparephosphinoborines aphosphonium salt is set forth in Table A below:

TABLE A Phosphqnium salt process Example No. Phosphonium Salt GramsBorohydrlde Grams Solvent 7 Product (omnnmrnuu 1.:2o A1(BH. fuoirrnnrnnnn. (C5H9)2H9PCL.. 1:23 LlBH4 (CsHg)rPBH q r 2P 3- a(QtHmPBHflaer NaPH' Preferably, the by product'H duced can be acceptedby passing the immiscible material for adsorption of the ammonia.Recommended,v

Example V. Bis(p-tolyl)phosphine in an amount 1.23 g.v and diborane inan amount of 0.14 g. were condensed in a nitrogen-filled 200 ml. flaskat -40 C. After formation of the phosphine borine addition product, thisThe.

Example VI.--Phosph ine in the-amoun t of 0.717 g.. (0.0211 mol) waspassed into a stirred solution of 0.4847 g. (0.02108 mol) Na dissolvedin a 1 liter quantity of refluxing ammonia (33.4 C.). The by-product,hydrogen, was vented'through a series of cold traps to catchtheunreacted PH and a. mercury bubbler was used to .prevent access ofair into the apparatus. A quantity of 1.3152 g. or 0.01935 mol .of (CHhCl was then added,

- ,the rate of addition being limited by the capacity of the a stirredsolution of the sodium dissolved in refluxing ammonia until the bluecolor is replaced by the yellow color I through a mercury bubbler'topreventaccess of;airinto the apparatus. Other suitable means forremoving the hydrogen; from the reaction vessel and preventing access ofair are known to the art and may beemployed. .An

alkyl halide having the general, formula (CH X wh ere a isv at least 2and-wherein X represents a halogen, is then added to the contents ofthereaction vessel until the yellow color is discharg V H be added asrapidly as permitted by the apparatus used, that is, as rapidly as thequantity of alkyl halide introreaction vessel. The product, ifsulficiently volatile at +33", is azeotropically distilled: from thereaction mixturewith the solvent and then freed of, residual ammoniaproduct layer through a suitable is anhydrous zinc sulfate at 0 C.--"The product is then purifiedby distillation. This procedure forseparating the solvent and the product is suitable if the desiredprodnot is sufliciently volatile at the boiling point of ammonia, -.-33.C. However, where the product is-high boiling,

it,.is distilled from the reaction vessel ,after evaporation of thesolvent'and thereafter purified by fractional distillation. i

ed. The alkyl halide may reflux condenser- -the addition continuinguntil the yellow color disappeared from the reaction mixture. Theproductwas relatively volatile at the boilingtpoint of ammonia, '-.33 C., andwas azeotropically'distilled from the reaction mixture with the solvent.Theimmiscible-produet layer was freed of residual ammonia by passing itthrough vanhydrous zinc sulfate at 0 C. and purified by distillae tion.A mixture of products was secured, 0.5754 g., or a yield of 45.5%, of(CH (PH and0.4129 g., or a yield of 45.3% 'of (CI-I hPH; Thedesiredheterocyclic. ring'phosphine-material was'separat ed from thedifunc tional phosphine by distill'ation under vacuum with a fractionaldistillation column having a vapor take-off head. Thereafter theheterocyclic phosphine material in a quantity of 0.4129 g. was placed ina 500ml.round bottom within the given volume of the flask previouslyflushed with nitrogen, cooled to C. and 0.0661 g. of diborane added. Theaddition compound which formed was heated under reflux .until furtherhydrogen no longer evolved. A quantitative yield of thecyclotetramethylenephosphinoborine,

wassecured. The trimeric form of this material melts at 169 C.

Examples V and VI above both relate to a process wherein aphosphineborine is pyrolyzed to yield the desired phosphinoborine.Stoichiometry relating to-additional examples utilizing this typeprocess is set, forth in Table B below: 7 V

TABLE B Pyrolysis of a phosphine borine Approxi- Example mate No.Phosphine Borine Pyrolysis Product Tempera-- ture, 9 C.-

vrr temm'cmmnr:BH,--.-..- 20o [(p-CeHfiqHOrPBHz]... VIIICsHs(CaH17)HP:BHs 250 [CsHKCsHrDPBHfl IX CHflCHzhHPFBHCHa): I a V I i i150, [(CH2)4PBH1] ..-[(0Ha)4PB(CH3)IJ-KOH MPBHCHAJ(copolyomwmnnmnm I X.e. CH QCBflpHPt?(CsH7):H... 230 [(C H2)QPB(CaH'Dfln'KCHDsPBHCzHfl,(copolymer).

mixture of productsis securedbyithe reaction, one of which is adifunctional phosphine having the formula (C H) (PI-I )g and the otherisftheheterocyclic ring including the phosphorus atom; having thegeneral. formula 65 v viously flushed with nitrogen. Diethyl ether-inthe amount.

of 20 ml. was added to the reaction flask. Triethylainine These twomaterials are then separated by fractional distillation, the cyclicphosphine being volatilized firstkf"The heterocyclicphosphorus-containing isif then reacted using any of the; generalprocedures is'et forth above for the-'preparationiof thfe "phosphiiie"borine ield' phosphino- Example XI.-Phenylmethylphosphinedimethylbromoborine, C H (CH},)HP:BBr(CH in the amount of 1.673 .g wasplaced in a ml. round bottom iflask pre-.

in the'amount of 0.707 g. was also added. Triethylam monium bromide wasfiltered, from the reaction mixture.

phinoborine desired. Stoichiometry for additional runsutilizingthis'type process is set forth in Table C below:

mers of various of the compounds, the method of prep aration of suchmaterials beingthat set forth above for In the examples which follow,the prepaartion of varil1s'"lln631 polymers is set forth-these materialsalready having been briefiy'alluded to earlier. Linear poly mers arephosphinoborine materials having at least one and possibly twohydroge'ns bonded to the phosphorus atom. They are phosphinoborines ofthe type where R, R and R" represent various organic radicals orhydrogen, at least one of these representing an aromatic radical.

As in the case with the other phosphinoborines described in detailabove, these hydrogen-bearing phosphinoborines may be prepared by thedehydrohalogenation of the corresponding phosphine haloborine. The

pyrolysis" method or the method involving reaction of aphosphoniumhalide with a borohydride (which also uses pyrolysis in its latterstages) may not be used as these will drive oh? the hydrogen subtendingfrom the phosphorus, thus producing a highly cross linked polymer whichis of little value; The dehydrohalogenation of phosphine haloborines toyield the materialshaving at least one hydrogen on the phosphorusproceeds as follows:

n(RH P:BRR"X)---+%(RHPBRR),,-lnHX wherein X is a halogen and the othersymbols are used in the fashion set out earlier.

The ring materials prepared from secondary phosphine substances whichare primarily the trimer with lesser amounts of the tetrarner and higherpolymers are predominantly solids at temperatures as high as 300 C.

individual phosphinoborines' excepting that mixtures precursors areprepared at" the outset.

We claim: l. A phosphinoborine polymer of ring configuration comprisinga plurality of phosphinoborine uni-ts, said polymer having the formula:

[-RR'PBR.'R"l,,

wherein R and R are selected from the class consisting, of (a) a singlepolymethylene group of from three tosix" carbons chain length bondedthrough its terminalcarbon atoms to the phosphorus atom-and (b) twoseparate radicals, said radicals being'selected fromtheclass:consistingof: alkyl groups havingless than 13 carbon" atoms, lowercycloalkyl, phenyl, IO'WCIfllkYl-SllbSiltlltGd phenyl, biphenyl andnaphthy-land wherein R" and-R are selectedfrom the class consisting ofhydrogen, lower. alkyl and phenyl,-at least one-of said symbols R, R, R

and R' representing a substituent selected from the class consisting ofphenyl, lower alkyl-substituted phenyl, bi

phenyl and naphthyl and wherein nis an integer fromboth. lower: alkyl.

and display extreme resistance to heat and are chemically stable. Sincethey also display excellent dielectric properties, they find utility asdielectrics where higher temperatures and opportunities for chemicalreaction (such as hydrolysis) are prevalent, where long chain aliphaticgroups (e.g., Q' -C are bonded to the phosphorus atom, the effects ofthe aromatic or alicyclic ring may be neutralized to a certain extentand the compounds may be liquids, at temperatures wherein they areadvantageously used (l0O-300 C.) and thus serve as chemicallyandthermally stable hydraulic fluids.

Phosphine borine materials are used in the examples set forth above in anumber of instances. It is to be understood that they may beprepared inaccordance with the procedure set out in our copending application,Serial No. 446,148, filed July 27, 1954, entitled, Phosphine BorineCompounds and Their Preparation, now abandoned.

Obviously many modifications and variations of the inventionashereinbefore setforth may be made without departing from the spiritand scope thereof, and therefore only such limitations should be imposedas are indi cated in the appended claims. For example, the invention-isnot limited to polymers of individual posph0rino-.

bofiiies, but, as serrate in the examples, includes copoly- 7. Aphosphinoborine polymer of ring configuration comprisinga plurality ofphosphinoborine units, said polymer having the formula wherein R and Rare selected from the class consisting of hydrogen, lower alkyl andphenyl, wherein x is an integer of from 2 to 5 and wherein n is aninteger of from 3 to 4 indicative of the degree of polymerization.

8. A phosphinoborine polymer of ring configuration comprising aplurality of phosphinoborine units, said polymer having the formula [(CI-I PBRR"'1",,; wherein. R" and1 R"are selected from the'classconsisting? of hydrogen, lower alkyl'and phenyl and wherein n' is aninteger of from 3 to 4 indicative of the degree of polymerization. V

9. A phosphinoborine polymer of ring configuration comprising aplurality of phosphinoborine units, said polymer having. the formula[R(C H )PBR"R"],, wherein'R is an. alkyl group of less than 13 carbonatoms. and wherein R" and R' are selected from the classconsisting. ofhydrogen, lower alkyl and phenyl and wherein. n is an integer of from 3m4 indicative of the degree of polymerization.

10. A polymer of the formula {(C HiQfiliHiL egree of polymerization.

yvhere n is an integer of from 3 to 4 indicative of the deg r'ee ofpolymerization.

13. A polymer of the general formula;

' 5) 2 1. wherein-n is an integer from} to 4 indicative of the degree ofpolymerization.

14. A polymer having the general formula:

' [C,H (CH )PBH:],, wherein n is an integer from 3 to v4' indicative ofthe de? gree of polymerization.

15. A polymer of the general formula;

geese-4e where n is an integer of from 3 to 4 indicative of the V 2. Apolymer of the formula [(CH C HQ PBI-Ql r 10 wherein a is ah integerfrom 3 m 4 indicative-of the 68* g ee of polymerization.

. i .16. A polymer of the general formula:

onxcmminnn.

wherein n is an integer from to 4 indicative of the degree ofpolymerization. 17. The copolymer having the formula I where the sum ofm and n is 3 and where in is 1-3 and n is 3 -1.

References Cited in the tile of this patent Burg et'aL: Amer. Chem.Jour., vol. 75, PP-

Hewitt et 211.: Chemical Society Journal (London),

" 20 pp. 530-534 (1953). Publ. February 1953; received in Patent OfficeLibrary April 1, 1953.

1. A PHOSPHINOBORINE POLYMER OF RING CONFIGURATION COMPRISING APLURALITY OF PHOSPHINOBORINE UNITS, SAID POLYMER HAVING THE FORMULA: